Abstract

The decay kinetics of photogenerated electrons in the water splitting reaction on a Pt/TiO2 photocatalyst was studied by time-resolved IR absorption spectroscopy. The decay of the photogenerated
electrons within 2 μs was decelerated when the catalyst was exposed to water vapor. The holes were consumed
by the reaction with water instead of by the recombination with the electrons. On the other hand,
the decay at 10–900 μs was accelerated by the exposure. The electrons were consumed by the reaction with
water. The rate of the hole-consuming reaction was independent of the pressure of water vapor, whereas
that of the electron-consuming reaction increased with the pressure from 1 to 10 Torr. The different pressure
dependences indicate different reactants involved in the oxidative and reductive reactants.